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Bacterial leaf spot of lettuce
| parent = Xanthomonas | image = File:Lettuce_Bacterial_leaf_spot_Xanthomonas_campestris_pv._vitans3.jpg | caption = | kingdom = Bacteria | phylum = Proteobacteria | class = Gamma Proteobacteria | order = Xanthomonadales | family = Xanthomonadaceae | genus = Xanthomonas | species = Xanthomonas campestris pv. vitians | synonyms = Bacterial leaf spot and head rot Bacterial leaf spot of lettuce Bacterial spot }} Bacterial leaf spot of lettuce caused by ''Xanthomonas campestris pv. vitians''Brown, N.A. (1918). Some bacterial diseases of lettuce. J. Agric. Res. 13:367-388. was first described in the United States by Nellie Brown in 1918 from diseased lettuce in South Carolina and Virginia. The disease was first reported in California in 1964.Schroth, M. N., Thompson, J. P., Bardin, R., and Greathead, A. 1964. Bacterial spot of lettuce. Calif. Agric. 18: 2-3. It has since been reported from the major lettuce growing regions worldwide probably due to contamination of seed.Sahin, F.; Miller, S A. (1997). Identification of the bacterial leaf spot pathogen of lettuce, Xanthomonas campestris pv. vitians in Ohio, and assessment of cultivar resistance and seed treatment. Plant Dis. 81:1443-1446.Umesh, K.C.; Koike, S.T.; Gilbertson, R.L. (1996). Association of Xanthomonas campestris pv. vitians with lettuce seed. Phytopathology 86:S3. In addition to survival on seed, the pathogen can survive in fields in plant debris and on leaves of symptomless weeds during fallow periods between lettuce crops.Barak, J.D.; Koike, S.T.; Gilbertson, R.L. (2001). Role of crop debris and weeds in the epidemiology of bacterial leaf spot of lettuce in California. Plant Dis. 85:169-178. Symptoms There are two discrete symptoms associated with bacterial leaf spot and head rot. The first include watersoaked, brown lesions that later turn black about 1-2mm (⅛in) in diameter occur. These lesions become V-shaped, translucent, and collapse.Toussaint, V. (1999). Bacterial leaf spot, a new disease of lettuce in Quebec caused by Xanthomonas campestris pv. vitians. Phytoprotection 80:121-125.Sahin, F.; Abbasi, P.A.; Miller, S.A. (1997). Variation among strains of Xanthomonas campestris pv. vitians in Ohio. Phytopathology 87:S84.Sahin, F.; Miller, S.A. (1998). Two new hosts of Xanthomonas campestris pv. vitians. Plant Dis. 82:262. Lesions may expand along the veins of the plant.Wallis, F.M.; Joubert, J.J. (1972). Bacterial leafspot of lettuce in Natal. Phytolactica 4:137-138. The second type of symptom consists of small black spots scattered along the leaf surface. Treatment There are no recommended bactericides. Pesticides allowed on other vegetables for control of bacterial diseases may reduce disease severity by only 50% of that observed on non-treated plants.Carisse, O. (1997). Essais de produits bactéricides pour la répression de la nécrose marginale de la laitue (Xanthomonas sjp. pv. vitians) in Journées horticoles provinciales, décembre 1997, Sherrington, Québec, Canada.Carisse, O.; Ouimet, A.; Toussaint, V.; Philion, V. (1999). Evaluation of the effect of seed treatments, bactéricides and cultivars on bacterial leaf spot of lettuce caused by Xanthomonas campestris pv. vitians. Plant Dis. (in press).Toussaint, V.; Carisse, O.; Philion, V. (1998). Repression of bacterial leaf spot of lettuce in the field. Trial Report. Agriculture and Agri-Food Canada, St-Jeansur-Richelieu, Québec, Canada.Toussaint, V.; Carisse, O.; Philion, V. (1999). Repression of bacterial leaf spot of lettuce in the field. Trial Report. Agriculture and Agri-Food Canada, St-Jeansur-Richelieu, Québec, Canada. Moreover, the use of some copper bactericides can cause symptoms of phytotoxicity on lettuce plants. Prevention For controlling bacterial leaf spot of lettuce, différent approaches must be considered. An integrated disease management program should include the use of résistant cultivars of lettuce, seed treatments, an early detection of the bacterium on seedlings, and a biological and/or chemical control to reduce the pathogenic bacterial population in greenhouses. Examples Lettuce_Bacterial_leaf_spot_Xanthomonas_campestris_pv._vitans1.jpg|Plant with a few individual bacterial leaf blight lesions. Lettuce_Bacterial_leaf_spot_Xanthomonas_campestris_pv._vitans2.jpg|Plant with many individual lesions. Lettuce_Bacterial_leaf_spot_Xanthomonas_campestris_pv._vitans3.jpg|Plant with individual lesions and small patches of coalesced lesions. Lettuce_Bacterial_leaf_spot_Xanthomonas_campestris_pv._vitans4.jpg|Plant with medium sized patches of coalesced lesions. Lettuce_Bacterial_leaf_spot_Xanthomonas_campestris_pv._vitans5.jpg|Plant with large patches of coalesced lesions. References Category:Disease Category:Lettuce diseases